Solid-state image sensing devices (camera modules) applied to cameras built in portable phones usually incorporate a solid-state image sensor, a signal processing device (DSP), a lens, a lens holder, a lens barrel, and other components in a package.
A mainstream of conventional solid-state image sensing devices are mainly single-focus types, however recently, there is an increasing demand for highly functioned solid-state image sensing devices of high pixel number and a high image quality. Portable phones are also in this trend nowadays. The solid-state image sensing devices built in portable phones have a high pixel number and functions such as zooming or automatic focusing due to an optical mechanism equivalently to a machine specialized for capturing an image, such as a digital still camera. Furthermore, the portability of the portable phones promotes integration of a semiconductor (sensor, IC for signal processing), a plurality of lens or an optical mechanism, driving devices (such as a motor) for driving the plurality of lens or the optical mechanism, and other components in the solid-state image sensing device.
A product cycle of the portable phone is however short, and the portable phones tend to quickly be changed to a next model. Therefore, the solid-state image sensing device to be installed to the portable phones requires to be manufactured in mass in a short period of time. In order to fulfill this demand, not only the product reliability, but also the easy assembling the solid-state image sensing device is an important factor.
Furthermore, it is important to satisfy the following two conditions in order to manufacture the solid-state image sensing device:    (a) an optical center of an image sensing surface of a solid-state image sensor is concentric to an optical axis of a lens; and    (b) a plane surface of the image sensing surface and the optical axis of the lens are orthogonal to each other.These conditions are the conditions required for a lens alignment with respect to the solid-state image sensor.
The conventional solid-state image sensing devices without the high functions easily satisfy the two conditions, even for small-sized, lightweight solid-state image sensing devices. However, the recent solid-state image sensing devices with the high-functions require accurate and highly precise structural members, and also require a highly defined receiving section of the solid-state image sensor. Therefore, in order to manufacture such solid-state image sensing devices, it is necessary to meet the two conditions more severely.
In addition, particularly for the solid-state image sensing devices applied to cameras built in the portable phones, compactness and reduction in weight are also demanded. Therefore, a complex compensation mechanism applicable to common cameras may not be applied to such solid-state image sensing devices.
Therefore, conventionally, the solid-state image sensing device is manufactured so that the aforementioned two conditions are satisfied, assuming that the solid-state image sensor is mounted parallel to the circuit board. Namely, the circuit board is the basis of the alignment. More specifically, an image sensing surface (receiving surface) of the solid-state image sensor and the circuit board of which the solid-state image sensor is to be mounted are assumed to be parallel (same) to each other. With this presupposition, the lens (or the lens holder) is mounted, based on a plane surface of the circuit board.
However, the actual circuit boards have manufacturing variation. Therefore, there is a limit in the precision in assembling and mounting the solid-state image sensing devices. Focusing adjustment (optical adjustment) after the assembling of the camera module is thus essential. The camera module also requires selection of the most appropriate material so as to satisfy its specification.
However, if the alignment is performed based on the circuit board, half blur of a focus may occur. The half blur denotes a state where the focusing of the image is uneven between a top and a bottom or a left and a right of the image. In addition, the focusing requires high-cost investment in plant and equipment, as well as manpower, and further requires considerable skill. Therefore, plenty of work hours are also required.
Each of Patent Documents 1 and 2, for example, discloses a solid-state image sensing device where the alignment is performed not based on the circuit board. FIG. 11 is a cross sectional view of the solid-state image sensing device of Patent Document 1. FIG. 12 is a cross sectional view of the solid-state image sensing device of Patent Document 2.
As illustrated in FIG. 11, a solid-state image sensing device 500 is subjected to alignment of a lens 511 with respect to a solid-state image sensor 524 in a part close to an image sensing surface of the solid-state image sensor 524. More specifically, in the solid-state image sensing device 500, positions of a transparent lid section 526 and a lens holder 510 are set by an adhesive applied on a joining section 520 on a surface of a transparent lid section 526.
As illustrated in FIG. 12, in a solid-state image sensing device 600, a glass substrate 626 is a sealing cover glass with a lens array, in which the glass substrate 626 itself has a condensing function and a image forming function. The glass substrate 626 is adhered on a solid-state image sensor substrate 620 by an adhesive layer 625 formed on the glass substrate 626. As such, in the solid-state image sensing device 600, the alignment of each of the substrates are performed referring to an alignment mark provided on a fringe section of each of the substrates.    Patent Document 1    Japanese Unexamined Patent Publication, Tokukai, No. 2004-301938 (published Oct. 28, 2004)    Patent Document 2    Japanese Unexamined Patent Publication, Tokukai, No. 2004-031499 (published Jan. 29, 2004)
However, it is difficult to say that the conventional solid-state image sensing devices satisfy the strictly required lens alignment precision. Therefore, in order to provide highly functional solid-state image sensing devices, it is necessary to further improve the lens alignment precision.
More specifically, in the solid-state image sensing device 500 of Patent Document 1, the alignment of the lens holder 510 is based on the surface of the transparent lid section 526. However, such alignment solely aligns the lens holder 510 with respect to the solid-state image sensor 524. Namely, the alignment precision of the lens 511 to the lens holder 510 is completely not considered. Therefore, it is difficult to say that the lens 511 is aligned in high precision. Particularly, if the alignment precision (precision of the holding position) of the lens 511 by the lens holder 510 is poor, the alignment precision of the lens 511 with respect to the solid-state image sensor 524 becomes poor.
In addition, the solid-state image sensing device 500 uses the surface of the transparent lid section 526 as the basis of the alignment. This makes it possible to attain alignment in a vertical direction (stacking direction), however cannot attain sufficient alignment in a plane direction (horizontal direction; direction perpendicular to the vertical direction).
In the solid-state image sensing device 500, a joining section 520 is provided on a peripheral part of the transparent lid section 526. Therefore, if the manufacturing variation (warp, bend) of the circuit board 521 is great, the alignment precision of the lens 511 also becomes poor. As a result, for example, if the variation of the circuit board 521 is in the horizontal direction (plane surface direction) of the transparent lid section 526, obviously the alignment precision of the lens 511 is also poor. If the warp or the bend of the circuit board 521 is great, the joining section 520 cannot be secured, thereby the alignment of the lens 511 is not possible.
As such, the lens alignment precision with respect to the solid-state image sensor is insufficient in the arrangement of Patent Document 1.
Furthermore, both of the solid-state image sensing devices of Patent Documents 1 and 2 have a fixed focal length (is a single-focused type). Therefore, the solid-state image sensing devices of Patent Documents 1 and 2 are not suitable for recent solid-state image sensing devices, which have the demand for high function. Particularly, the solid-state image sensing device 600 of Patent Document 2 has an object to reduce size and improve reliability of the solid-state image sensing device. The object is attained by mounting no optical member on the solid-state image sensing device 600. The optical member is unnecessary due to use of the glass substrate 626 which possesses the condensing function. Therefore, an addition of a zooming function or an automatic focusing function would contradict with the object. That is to say, an object of the solid-state image sensing device 600 of Patent Document 2 is to address a problem unique to an arrangement where a microlens is equipped on the image sensing surface of the solid-state image sensor 624. The lens alignment with respect to the solid-state image sensor 624 is not an object of the solid-state image sensing device 600 in the first place.